Electrical measuring instrument.



3 SHEETSSHBET 1.

PATENTED OCT 3, 1905.

E. F. NORTHRUP; ELEGTRICAL MEASURING INSTRUMENT. APPLICATION FILED NOV.19,1904.

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PATENTED OCT. 3, 1905. E. P. NORTHRUP.

APPLICATION FILED NOV 19, 1904.

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u I 1 i I 7 ELECTRICAL MEASURING INSTRUMENT.

PATENTED OCT. 8, 1905.

E. P. NORTHRUP. I ELECTRICAL MEASURING INSTRUMENT. PPPPPPPPPPPPPPPPP mi19, 1904.

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EDIVIN F. NORTH RUP,

OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE LEEDS AND NORTHRUPOOMPANY,

OF PHILADELPHIA, PENN- SYLVANIA, A CORPORATION OF PENNSYLVANIA.

ELECTRICAL MEASURING INSTRUMENT.

and the like in which the current'isindicatedor detected or themeasurement made by the movement of a coil system in a magnetic field;and the principal objects of the invention are to so choose themechanical arrangement of the parts that a suspended system may be usedwith freedom from danger of breakage, to compress the instrument intothe smallest possible space in a vertical direction, and to so choosethe shape of what is designed to provide the magnetic field that thesimplest form of construction may be employed, so that if this be amagnet a single casting will suffice.

Another object of this invention is to increase the tensile strength ofthe suspension by the employment of a plurality of filaments 3 placedside by side without increasing the torsion to anything like the sameextent that it would he were the same tensile strength gained by theemployment of a single filament of increased diameter.

\Vith the above objects in view, and others which will hereinafterappear, my said invention consists in the novel combination andarrangement of parts herein described, and pointed out in the claims, inwhich latter I 0 employ the expression electrical measuring instrumentin its broader sense to cover detector-galvanometers and instrumentsdesigned to indicate the presence of current, as well as instrumentswhich actually measure the same.

By this invention I am enabled to produce an instrument of extremesimplicity and compactness, while at the same time preserving thesensitiveness and general efficiency of 5 other forms which it hashitherto been considered impracticable to make so simple andSpecification of Letters Patent. Application filed .Iovember 19, 1904.Serial No. 233,454.

Patented Oct. 3, 1905.

compact. In other words, I combine the compactness and simplicity ofsingle-magnet pivoted coil instruments with the sensitiveness anddelicacy of those which employ a suspended system.

Referring to the accompanying drawings, which form a part of thisspecification, and in which is illustrated one form of my said inventionand modifications thereof, Figure 1 is a top plan view of a portablegalvanometer embodying my invention; Fig. 2, a central verticallongitudinal section through the containing box, showing a portion ofthe magnet'broken away; Fig. 3, a section on line 3 3, Fig. 1, showingthe magnet system in elevation; Fig. 4, a detail top plan view of thefour-coil suspended-system; Fig. 5, a central cross-section of the same;Fig. 6, a detail section of a modified form of suspension-terminal; Fig.7, a detail plan view of one of the guards for limiting the sidewisemovement of the suspended system; Fig. 8, a front elevation of the same,and Fig. 9 an end elevation of the same; Figs. 10, 10, and 10 diagramsof different forms of coil systems and magnets. Figs. 11 to 15,inclusive, illustrate a modified form of galvanometer embodying myinvention, in which Fig. 11 is a top plan view of the coils of themoving system; Fig.

12. a top plan view of the galvanometer removed from its containing-box;Fig. 13, an end elevation of the same; Fig. 14:, a central l 2, as willbe seen, is

vertical longitudinal sectional view of the same; and Fig. 15, a sectionon the line 15 15, Fig. 14:, looking in the direction of the arrow.

In carrying out the form of my invention shown in Figs. 1to9 I employasubstantially U-shaped cast-iron permanent magnet 1, cast in one piece,having inwardly-directed poles at one end, so as to have north polarityonly on one side of the air-gap separating the poles and south polarityonly on the other side of the air-gap, all the magnetic lines of forcepassing between the poles being therefore in substantially the samedirection. This magnet is slotted, as at 2, to accommodate a suspendedcoil system 3, mountedfor movement between the poles of said magnet andadapted to impart motion to the pointer 41:. The slot purely formechanical purposes. The magnetic action would be the same if the slotwere not therethat is, it would be just the same if there were a singlepole-face on each side of the air-gap, as shown in dotted lines in Fig.10, instead of two, as shown in Figs. 2 and 3.

The movable system consists in the present case of four coils 5 of veryfine wire wound alternately in opposite directions, so as to producealternate north and south poles when viewed from one side, as shown inthe diagram Fig. 10. These coils are spaced with their centerspreferably ninety degrees apart and all lie in thesame(preferablyhorizontal) plane, being held between two disks ofaluminium or other non-magnetic metal 6. These disks while supportingthe coils act also to damp the system and render it practicallydeadbeat. The coils are clamped tightly between the disks 6 by means ofa flanged screwthreaded spindle 7 and a flanged nut 8. The lower shankof the spindle 7 is split, as at 9, the portion 10 being insulated fromthe main shank, as at 11. These split portions are bound together bysuitable insulating material 12. A separating-collar13,ofinsulatingmaterial, is inserted between the disks 5 and surroundsspindle 7. ires let and 15, leading to and from the coils 5, areconnected, respectively, to the spindle 7, through the nut 8, and to theinsulated portion 10 of the spindle, all as shown most clearly in Fig.5.

l Vhether there be two coils or a greater number employed, ashereinafter described, it is preferable that the pole-faces of themagnet be so shaped and so placed above and below the plane of the coilsthat at all times approximately half of the coil-surface will be betweenpole-faces and half not between pole-surfaces. (See Figs. 10 and 10.)

The system is suspended by a line wire or condacting-filament 16, whichis soldered at one end to the end 17 of the spindle 7 and at its otherend to a coil-spring18, secured at its upper end to a plug 19. carriedby a hollow adjusting-head 20, in which the spring 18 is also carried.(See Fig. The adjustinghead 20 is mounted to turn in the upper end of ametal tube 21, screw-threaded into the magnet at its lower end, as at22. This adjusting-head is provided with an annular groove 23, whichextends a part of the way around it, and into this groove extends theend. of a screw 24, which, engaging the end of the groove, acts to limitthe extent to which the adjusting-head may be turned, and thereforeprevents the suspension wire orfilament from being twisted off byturning the adjustinghead too far. The plug 19 is held from turning inthe head 20 by the set-screw 25. To the end 26 of the member 10 of thesuspended system is soldered a line wire or conductingfilament 27,similar to the filament 16, and the lower end of this filament 27 issoldered to the end of a fiat spring 28, made fast at one end by screws29 to the bottom of the magnet and insulated therefrom, as at 30. Thefilament 27 is of such length that the spring 28 will keep it taut.

In order to prevent the spring 28 by its inertia from breaking thefilament 27 or both filaments, a limiting-screw 29 is provided. Thisscrew passes through an opening 28 in the spring and is screwed into themagnet, as shown. The head of the screw acts to limit the downwardmovement of the spring.

Instead of using single-strand filaments 16 27 I may employ a pluralityof filaments arranged side by side, as shown in Figs. 13 and 14: andhereinafter more particularly described.

In order to limit the sidewise movement or play of the suspended systemthat is, the

movement of the system out of the line of its suspensionand thus toguard against the liability of the suspension-filaments to become brokenby shocks which the instrument may receive. I provide two guard-pieces31 and 32, secured by screws 38 and 34: or otherwise to the ends of themagnet 1. These guards consist each preferably of metal stamping havingwings 35, with holes 36 made elongated for adjustment and adapted toreceive the attaching-screws, and an extension 37, bent at right anglesto form the portions 38, which portions are provided each with anopening 39, into which leads a slot 40. The ends of the suspended systemextend through the openings 39 of these guards, with a slightclearancebetween the spindle of the system and the guards. By means of thisarrangement the system is allowed to turn or oscillate freely around theaxis of its suspension; but its sidetoside movement is limited by theguards, thus greatly reducing the liability of a sudden jolt or shock tobreak the fine suspension-iilaments.

The movement of the system vertically is limited bythe pole-faces of themagnet, thereby affording an additional means to prevent the breaking ofthe filaments.

The suspended system, mounted as described, is accurately balanced, sothat the instrument may be used in a slanting position as well as in ahorizontal or level position.

Upon the upper face of the magnet is a suitable scale 41, over which thepointer 4 is adapted to move, the magnet being provided with an opening42 to admit of the required movement of the pointer.

The scale over which the pointer moves may be calibrated up to a certainnumber of divisions on each side of the zero, so that up to this limitthe gal vanometer will serve as a direct reading measuring instrumentwhen its constant has been once determined.

The instrument thus constructed is mounted in a suitable box or casing43, to the top of which the magnet is made fast, as by screws 14, whichpass through the top into the magnet, the adjusting-head 20 extendingthrough the top, as shown, so that the pointer maybe adjusted withoutremoving the cover.

The scale is adapted to be read through a circular opening 45 in the topof the box, the said opening being provided with a glass top &6, helddown by a brass ring 47.

The binding-posts 18 49, mounted upon one end of the box-top, form theterminals of the electrical circuits of the instrument, which may betraced as follows: from the bindingpost 18 by wire to the spring 28,thence by conducting-filament 27 to insulated member 10 of the suspendedsystem, wire 15, coils 5, wire 1 1, nut 8, and spindle 7 toconductingfilament 16, thence through spring 18 into adjusting-head,tube 21, magnet 1, and thence by wire 51, connected to said magnet, backto binding-post 4E9.

WVhen the current traverses the system as described, the coils willbecome polarized, as shown in the diagram Fig. 10that is. adjacent coilswill have opposite polarity when viewed from the same side. Thereforethe north-pole faces of the permanent magnet 1 will repel the north-polecoils and attract the south-pole coils and the south-pole faces of themagnet will repel the south-pole coils and attract the north-pole coils,so that rotation or partial rotation will be imparted to the system inthe direction of the arrow at the bottom of Fig. 10. Obviously whencurrent passes through the coils in the opposite direction from theabove the movement of the system will be in an opposite direction. Inthis connection it will be observed that the direction of the magneticflux or lines of force through the coils will be substantially at rightangles to the plane in which the coils move.

A galvanometer differing somewhat in construction from the one justdescribed, but embodying the essential principles thereof, is shown inFigs. 11 to 15. In the latter formthat is, as illustrated in Figs. 11 to15 -1 employ two elongated coils instead of four coils, as in the formercase. These coils 5 are, as in the former case, clamped between twoaluminium plates 6 and suspended in substantially the same manner,except in the latter case I have shown the system suspended by aplurality of filaments 16 and 27, though the single-strand filamentsuspension may be employed in this form of instrument, as in the firstform described. There is, however, a distinct advantage gained in usingthe multiple-strand suspension where it is desired to increase thetensile strength. The multiplestrand suspension admits of an increase intensile strength without increasing the torsion to anything like thesame extent that it would be increased were the increase in tensilestrength gained by simply employing a single filament of increaseddiameter. This will be more apparent when it is understood that thetorsion is proportional to (P where d is the diameter, while the tensilestrength is proportional to (Z The pointer is secured at one end toastrip of insulating material t, made fast between the coils, as shownmost clearly in Fig. 11.

The magnet in the form of instrument shown in Figs. 11 to 15 has twopole-faces, between which the systemis suspended in such manner thatnormally-that is, when not defiected-only a portion of both coils extendinto the air-gap between the poles, though at all times only aboutone-half of the coil-surface is between the pole-faces. On account ofthis arrangement of the coils the suspension-terminal is mountedslightly forward of the magnet-poles, for which purpose the magnet isprovided With an extension 1. The front of the magnet is slottedvertically, as at 1 to accommodate the suspended system. The coils ofthe system are wound in opposite directions, so that when currenttraverses them they will produce poles of opposite polarity when viewedfrom the same side. One of the coils will then swing around to inclosethe greatest number of lines of force, while the other coil will berepelled, the movement of the said coils depending upon the direction ofthe current entering the same.

The principle of the invention is not altered by the number of coilsemployed. Thus I may use a single magnet and one coil system, as shownin Fig. 10", where 1 represents one pole of a magnet and 3 a one-coilsystem suspended or pivoted at a point 3 On the other hand ,a largenumber of coils-eight, for example, as shown in Fig. 10may be used, whenthe pole-face of the magnet may be made of the shape shown in dottedlines 1" or other suitable shapes, as may be desired. Vhile l have shownand described a form of my invention in which a permanent magnet is usedto produce the magnetic field, the invention is equally applicable whenalternating currents are to be measured or indicated, in which case thefield would be produced by a coil or coils instead of by a permanentmagnet.

A modified form of suspension-terminal is shown in Fig. 6. In thislatter form the filament 16 is connected to a plunger 52, having atubular stem 53, surrounded by a coil-spring 54:. The plunger and springare carried in a hollow plug 55, the upper end of which is closed by ascrew 56. This hollow plug 55 fits into the adjusting-head 57 and isheld fast therein by the set-screw 58. The adjustinghead 57 fits intothe end of a tube 21, carrying a screw 2 1, which extends into anannular slot 23 in the adjusting-head for the purpose of limiting therotation thereof as described with relation to Fig. 3, the said slot 23extending only a part of the way around said head.

My invention is susceptible to other modifications without departingfrom the spirit thereof; but

\Vhat I claim is-- '1. in an electrical measuring instrument,thecombination with a single held-magnet having a plurality oi polefaces ofnorth polarity only on one side of the air-gap separating the poles ofsaid magnet and a 'ilurality of pole-faces of south polarity onlyopposite said north poles, 01 a Hat coil system supported to move insaid air-gap in a plane substai'itially at right angles to the directionof the magnetic lines of force between the poles of said magnet.

2. In an electrical measuringinstrument, the combination with a singlefield-magnet having a plurality of pole-Faces of north polarity only onone side of the air-gap separating the poles of said magnet, and aplurality of pole-tacos of south polarity only opposite said northpolefaces, of a suspended coil system adapted to move in said air-gap in aplane substantially at right angles to the direction of the magneticlines of force passing between the poles of said magnet.

3. In an electrical measuring instrument, a single field-magnet, amovable coil system comprising a plurality of coils suspended to lie ina plane substantially at right angles to the direction of the lines offorce passing between the poles of said magnet, said coils being soarranged relative to the poles of said magnet that in the position of nodeflection, approximately one-half of each coil will be between oppositepole-faces and at all times a portion only 01'' the coil area will bebetween opposite pole-faces.

at. In an electrical measuring instrument, a single liel(il-magnet, amovable coil system comprising a plurality of flat coils suspended tolie and move in a plane substantially at right angles to the directionof the lines of force passing between the faces of said magnet, saidcoils being so arranged relative to the poles of said magnet that in theposition of no deflection, approximately one-half of each coil will bebetween opposite pole-faces and at all times a portion only of the totalcoil area will be between opposite pole-faces.

5. In an electrical measuring instrument, the combination with afield-magnet, of a coil system mounted for movement in the fieldot-said. magnet in a plane substantially at right angles to thedirection of the lines of force passing between the poles of saidmagnet, said system comprising two elongated coils mounted side by sidein the plane of their movement, a portion only of each of said coilsextending into the lield of said magnet in the position of nodeflection, approximately onehalf of the coil area of said system beingat all times between opposite pole-faces of said magnet.

6. In an electrical measuringinstru ment, the

combination with a field-magnet having elongated pole-l aces, ot' a coilsystem mounted for movement in the lield of said magnet between saidpole-faces, said coil system comprising two elongated oppositely-woundcoils mounted side by side in the same plane substantially at rightangles to the direction 01 the lines of force of said magnet, said coilsbeing so mounted that their major axes are substantially at right anglesto that of the pole-faces of the magnet, with a portion only of thelength of both of said coils extending into the lield of said magnet inthe position of no deflection, and arranged to move so that one of saidcoils will move into the field of said magnet and the other recedetherefrom when current traverses said coils, substantially as described.

7. In an electrical measuring instrument, spring-terminals, a movablecoil system, means to suspend saidsystem between said spring-terminals,guards to limit the movement of said system out of the line of itssuspension, and a held-magnet acting to limit the movement 01 saidsystem in the direction of its line of suspension, said magnet having apole-face on each side of the plane of said coil system.

8. in an electrical measuring instrument, a tube, a hollow plug mountedto turn in the end of said tube, means to limit the turning movement ofsaid plug, a second plug mounted in the lirst, a suspension-iilament,and a spring connection between said lilament and said second plug.

9. In an electrical measuring instrument, a tube, a hollow plug mountedto turn in the end of said tube, means to limit the turning movementoi'said plug, a second hollow plug mounted in the lirst, and means to holdthe second plug fast within the first, a plunger mounted in the secondplug, a spring between said plunger and said second plug, and asuspension-lilament connected to said plunger.

10. in an electrical measuring instrument, the combination with a singlepermanent magnet, of a coil system consisting of a plurality of flatcoils mounted in a common plane, resilient suspension-terminals, meansfor suspending said coil system between said terminals so that saidcoils may have a deflective movement in the field of said magnets in aplane substantially at right angles to the direction of the lines offorce, the pole-faces of said magnet acting to limit the movement ofsaid system in the direction of the line of its suspension, and guardsto limit the movement thereof in a direction at right angles to the lineof suspension, substantially as described.

11. In an electrical measuring instrument,

the combination with a single permanent magnet, of a coil systemconsisting of a plurality of flat coils mounted in a common plane,resilient suspensioil-terminals, means for suspending said coil systembetween said terminals so foo IIO

that said coils may have a deflective movement in the field of saidmagnets in a plane substantially at right angles to the direction of thelines of force, the pole-faces of said magnet acting to limit themovement of said system in the direction of the line of its suspension,guards to limit the movement thereof in a direction at right angles tothe line of suspension, and a non-magnetic metal disk mounted to move inthe field of said magnet with said coils and to damp their movement,subtially as described.

12. In an electrical measuring instrument, the combination with a singlefield-magnet, of a flat coil system suspended for movement between thepoles of said magnet in a plane substantially at right angles to thedirection of the lines of force passing between the poles of saidmagnet, a scale mounted on the top of the said magnet, and a pointercarried by said movable system and adapted to pass over said scale.

13. In an electrical measuring instrument, the combination with asubstantially U-shaped bipolar cast-iron field-magnet. cast in one piecewith inwardly-extending pole-pieces at one end, of a coil systemsuspended for deflective movement between the poles of said magnet in aplane substantially at right angles to the lines of force 'iassingbetween said poles.

1st. In an electrical measuring instrument, an inelosing box or casinghaving an opening in its top, of a transparent covering for saidopening, a magnet mounted in said box, asuspension-terminal extendingthrough the top of said box and provided at its end outside of said boxwith an adjusting-head. a coil system suspended from said terminal fordeflective movement between the poles of said magnet in a planesubstantially at right angles to the direction of the lines of forcepassing between the poles of said magnet, a scale mounted on the upperface of said magnet and beneath said opening, and a pointer carried bysaid system and arranged to move over said scale.

15. In an electrical measuring instrument, the combination with asuspended flat coil system, of a magnet having facing pole-piecesbetween which the said system is adapted to have deflective movement,the pole-pieces of said magnet being located on opposite fiat sides ofsaid coil system, and also on opposite sides of said suspension.

16. In an electrical measuring instrument, the combination with asuspended fiat coil system. of a magnet having facing pole-piecesbetween which the said system is adapted to have dellective movement,the pole-pieces of said magnet being located on opposite fiat sides ofsaid coil system, and also on opposite sides of said suspension, a scalecarried above the magnet, and a pointer carried by said moving systemand adapted to move over said scale.

17. In an electrical measuring instrument, a flat moving coil systemcarried by torsional conductingsuspensions extending between twosupports arranged to yield in the direction of the line of suspension,and a magnet having t'acing pole-pieces between which the said system isadapted to have defi ective movement, the pole-pieces of said magnetbeing located on opposite flat sides of said coil system, and also onopposite sides of said suspension.

18. In an electrical measuring instrument, a flat moving coil systemcarried by torsional conducting-suspensions extending between twosupports arranged to yield in the direction of the line of suspension,and a magnet having facing pole-pieces, between which the said system isadapted to have deflective movement, the pole-pieces of said magnetbeing located on opposite sides of said coil system, reckoning in thedirection of the line of suspension, and also on opposite sides of saidsuspension, all of the windings of said system being at all times actedon by said magnet during the operation of the instrument, a scalecarried above said magnet, and a pointer carried by said system andadapted to move over said scale.

19. In an electrical measuring instrument, the combination with amovable system, a multiple suspension therefor consisting of a pluralityof filaments lying substantially parallel and having a tensile strengthequal to the sum of the tensile strengths of each of the filaments and atorsional force per unit of length less than would be the torsionalforce if the same cross-section of material were combined in a singlefilament, the several filaments of said suspension being adapted toconvey current in the same direction.

20. In an electrical measuring instrument, a field-magnet, a movablesystem, a plurality of torsional condnoting-suspensions in parallelcontact and supporting said system from both sides, between the poles ofsaid magnet, and yielding supports to which the ends of said suspensionsare secured.

21. In an electrical measuring instrument, a field-magnet having facingpole-pieces, a coil system, tWo spring-supports, one of which isangularly adjustable for the angular adjustment of said coil system, andmeans to suspend said coil system between said spring-supports fordefiective movement between the poles ot said magnet.

22. In an electrical measuring instrument, a field-magnet having facingpole-pieces, a coil system,two spring-supports, means to suspend saidcoil system between said supports for defiective movement between thepoles of said magnet, an index carried by said moving system, a scaleover which said index is adapted to move, an inclosing case, and meansoperative from the outside of said case for angularly adjusting one ofsaid spring-supports and therethrough the moving coil system and Imagnet, anda stop arranged to limit the move- IO index. ment of saidsystem out of the line of its sus- 23. In an electrical measuringinstrument, pension.

a lield'magnet having facing pole-pieces, a coil In testimony whereof Iaffix my signature in system, two spring-supports, one of which ispresence of two Witnesses.

angularly adjustable for the angular adjust- I ED\V1N F. NOR HRUP.

mentof said coil system, means to suspend said Witnesses:

coil system between said spring-supports for JOHN B. HuNKELs,

defiective movement between the poles of said Jos. \VALKER.

